It would be smart enough, but how long would it take before the coin gets any value.
correct me if I have misunderstood something
It would probably not have value since you would be the only user. But it
would have only 25 GH/s, and you'd have quite a lot of the coin.
okey, so the number of miners determines the value of the coin.
Would it be possible to lock the difficulty so that with a maximum of 25GH / s, only 20 coins per month could be mined.
The above is only an exemple.
The value of the coin is determined by what people are willing to pay for it. I could create some coin, get a million miners mining it, but if no one wants to buy my coin, then it is worthless. The number of miners is unrelated to the price. I'm not sure what you mean by a max of 25 GH/s with a max of 20 coins to be mined, but you can change the difficulty every block to adjust for the hashrate so that 20 coins, or a number close to 20 are mined in a month total.
If you are trying to get some money from your miner, maybe mine new SHA-256 coins that aren't on exchanges and hope they are listed?